It is known that lubricants become less effective during their use due to exposure to the operating conditions of the device they are used in, and particularly due to exposure to by-products generated by the operation of the device. For example, engine oil becomes less effective during its use, in part due to exposure of the oil to acidic and pro-oxidant byproducts. These byproducts result from the incomplete combustion of fuel in devices such as internal combustion engines, which utilize the oil. These byproducts lead to deleterious effects in the engine oil, and so, on the engine as well. The byproducts can oxidize hydrocarbons found in the lubricating oil, yielding carboxylic acids and other oxygenates. These oxidized and acidic hydrocarbons can then go on to cause corrosion, wear and deposit problems.
Base containing additives are added to lubricants in order to neutralize such byproducts, thus reducing the harm they cause to the lubricant, such as an engine oil, and so to the device, such as an engine. Over-based calcium or magnesium carbonate detergents have been used for some time as acid scavengers, neutralizing these byproducts and so protecting both the lubricant and the device. However, over-based phenate and sulfonate detergents carry with them an abundance of metal as measured by sulfated ash. New industry upgrades for diesel and passenger car lubricating oils are putting ever decreasing limits on the amount of sulfated ash, and by extension the amount of over-based detergent, permissible in an oil. A source of base that consists of only N, C, H, and O is extremely desirable.
Basic amine additives are an alternative to ash containing over-based metal detergents, in particular alkyl and aromatic amines. However, the addition of basic amine additives can lead to additional detrimental effects. For example, it is known that alkyl and some aromatic amines degrade fluoroelastomeric seals materials. These basic amine additives, such as succinimide dispersants, contain polyamine head-groups, which provide the source of base to the oil. However, such amines are believed to cause dehydrofluorination in fluoroelastomeric seals materials, such as Viton seals. This is a first step in seals degradation. Seal degradation leads to seal failure, such as seal leaks, which harms engine performance and also can cause engine damage. Generally, the base content, or total base number (TBN), of a lubricant can only be boosted modestly by such a basic amine before seals degradation becomes a significant issue, limiting the amount of TBN that can be provided by such additives.
There is a need for additives that deliver ash-free base to a lubricant without causing detrimental effects. In particular, there is need for basic amine additives that deliver ash-free base to engine oil without increasing seals degradation and/or impairing seal compatibility.
U.S. Pat. No. 2,390,943 relates to compositions comprising hydrocarbon oil and a combination of stabilizing ingredients.
U.S. Pat. Nos. 2,369,090 and 3,856,690 relate to lubricants which are stabilized against oxidative degradation.
U.S. Pat. No. 3,642,632 relates to lubricant compositions having improved resistance to deterioration under high performance conditions and is focused on gas turbine engines, such as turbojet, turboprop and turbofan engines.
U.S. Pat. No. 2,771,368 (Thompson, Nov. 20, 1956) relates to the use of N-substituted trialkoxy anilines as stabilizers for organic compounds, including fuels, mineral oils, and lubricating oils.
U.S. Pat. No. 4,234,434 (Wulfers, Feb. 14, 1979) relates to the use of dialkylanilines as stabilizers for hydrocracked oil.
WO/PCT application 2010/107882 (Preston et al., Sep. 23, 2010), relates to the use of anthranilic acid derivatives as ash-free amine-derived sources of basicity that do not cause harm to seals.
United States application 2010/0160195 (Cheng et al., Jun. 24, 2010) relates to lubricating compositions comprising derivatives of N,N-dialkylated aniline as ash-free boosters of total base number (TBN).
It has now been discovered that sulfurized aromatic amine compounds may be added to lubricants, such as engine oil, to deliver base. These additives surprisingly do not cause the harm to seal performance and corrosion that one skilled in the art would expect from such basic amine additives.